<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .box {
            position: relative;
            animation: box .5s;
        }

        @keyframes box {
            from {
                left: -20px;
            }
            to {
                left: 0px;
            }
        }
    </style>
</head>
<body>
    <div class="box" style="display: none;">323</div>
    <button class="test">test</button>
    <script>
        const test =  document.querySelector('.test');

        test.addEventListener('click',function() {
            const box =  document.querySelector('.box');
            box.style.display = "block"


        },false)

    </script>
</body>
</html>